Strength Between Bis-Acryl Resin and PMMA Utilizing Various Bonding Agents

Lining Bis-Acryl interim resins with flowable composite is performed, but methods to enhance bonding to PMMA are unknown.

Objective: To compare the effects of bonding agents in joining a Bis-Acryl temporary material to a PMMA interim product.

Method: Cylindrical-shaped specimens (9mm diameter, 10mm thick) of a commercial, self-cured Bis-Acryl resin (ProTemp) were prepared and embedded in self-curing PMMA. Specimen ends were polished to 1000 grit SiC,  air-particle abraded (50µm aluminum), and acid-etched (37% phosphoric acid). Specimens were divided into 5 groups (n=20 each), with each group receiving a different bonding agent prior to attachment of a self-curing PMMA cylinder (Jet Acrylic): Control: (mfg-recommended) Scotchbond universal applied and flowable composite resin was bonded instead of PMMA; Group M - MMA monomer application only; Group SU - Scotchbond Universal; Group SMP - Scotchbond Multipurpose; Group ENA - ENA Temp Bonding Fluid. After bonding agents were applied, a self-curing PMMA cylinder (2mm diameter, 2.5mm long) was bonded to the surface of the treated surface utilizing a mold and positioning device: Control Group bonded a flowable composite cylinder. Specimens were stored at room-temperature for 24h prior to testing, and were tested in shear (Ultradent Tester) at a crosshead speed of 1 mm/min. Peak load at failure was noted and converted into shear stress. Data were subjected to a 1-way ANOVA and the Tukey post-hoc test at a pre-set alpha of 0.05.

Result: Table presents mean shear bond stress values (MPa).

Control treatment produced significantly higher shear bond stress than all other methods. When bonding PMMA to Bis-Acryl, use of ENA demonstrated significantly greater stress than did use of methyl methacrylate monomer (M) only.

Conclusion: No bonding agent or treatment provided bond strength values of an interim PMMA material to a Bis-Acryl surface as high as did use of bonding a flowable composite to Bis-Acryl.